Date: Wed, 12 Feb 2020 15:56:46 -0500 From: Rich Felker <dalias@...c.org> To: "A. Wilcox" <awilfox@...lielinux.org> Cc: musl@...ts.openwall.com Subject: Re: bug#39236: coreutils cp mishandles error return from lchmod On Wed, Feb 12, 2020 at 01:59:09PM -0600, A. Wilcox wrote: > On 12/02/2020 13:07, Rich Felker wrote: > > On Wed, Feb 12, 2020 at 08:05:55AM -0500, Rich Felker wrote: > >> On Wed, Feb 12, 2020 at 12:50:19PM +0100, Florian Weimer wrote: > >>> * Paul Eggert: > >>> > >>>> On 1/22/20 2:05 PM, Rich Felker wrote: > >>>>> I think we're approaching a consensus that glibc should fix this too, > >>>>> so then it would just be gnulib matching the fix. > >>>> > >>>> I installed the attached patch to Gnulib in preparation for the upcoming > >>>> glibc fix. The patch causes fchmodat with AT_SYMLINK_NOFOLLOW to work on > >>>> non-symlinks, and similarly for lchmod on non-symlinks. The idea is to > >>>> avoid this sort of problem in the future, and to let Coreutils etc. work > >>>> on older platforms as if glibc 2.32 (or whatever) is already in place. > >>> > >>> The lchmod implementation based on /proc tickles an XFS bug: > >>> > >>> <https://sourceware.org/ml/libc-alpha/2020-02/msg00467.html> > >> > >> Uhg, why does Linux even let the fs driver see whether the chmod is > >> being performed via a filename, O_PATH fd, or magic symlink in /proc? > >> It should just be an operation on the inode. > > > > OK, I don't think it's actually clear from the test that the use of > > the magic symlink is the cause. It's plausible that XFS just always > > returns failure on success for this operation, and I don't have XFS to > > test with. > > > My root fs is XFS, but I only have musl to test with. Is there a test > case I can run on musl to determine the behaviour of XFS for you? > > The only glibc distribution that supports my platform is Void, so I > don't know if the Void glibc spin in a chroot would be sufficient if > there is no way to do this from a musl system. We've since found (in the other thread musl list isn't CC'd on) that this does not seem to be XFS-specific but happens in ext4 too, and is probably a high level vfs bug. Rich
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